Controlled Synthesis And Luminescence Properties Of Highly Luminescent Cesium Lead Halide Perovskites

All-inorganic lead halide perovskites have gained considerable attention owing to their high-performance in photophysical properties.There are three forms as follows:single crystal,polycrystal film and nanocrystals,the last two kinds of which are mainly used for optoelectronic devices.Currently,producting highly luminescent,nearly pinhole-free,all-inorganic perovskite films through a simple one-step solution process remains challenging.For all-inorganic perovskite nanocrystals?NCs?,although the room-temperature photoluminescence quantum yields?PLQYs?of these NCs in the green?CsPbBr₃?and red?CsPbI₃?spectral range approach unity,the PLQYs in the violet are much lower.Therefore,this thesis aims to:1)investigate a new method to synthesize high-luminescence,nearly pinhole-free CsPbBr₃ films,and provide a detailed investigation of the crystallization control of inorganic perovskite films;2)develop a new strategy to prepare high violet emission of CsPbCl₃ NCs and investigate its doping mechanism.Detailed results are as follows.Firstly,we have invesitigated the spin-coating temperature,commonly described as“room temperature”and regarded as an insignificant factor,which plays a paramount role in influencing the crystal-growth kinetics and film morphology,and revealed that CsPbBr₃ films own high luminescent prepared under low coating temperature.It's the reason that a one-step fabrication process for CsPbBr₃ film has poor repeatability.The experiment results show that CsPbBr₃ films prepared under different spin-coating temperatures experience different thermal histories,which influences the crystallization process and then causes huge gap in optical properties of CsPbBr₃ films.Additionally,we also reveal that polyethylene glycol?PEG?can be used for further tailor the crystallization process based on cold-casting approach,which enables the attainment of nearly pinhole-free CsPbBr₃ films with a maximum PLQYs of³0%.Benefiting from this,amplificant spontaneous emission?ASE?with a low threshold can be accomplished.Next,it's the first time that we report a general strategy,referred to as high-temperature injection method,for the synthesis of all-inorganic violet-emitting perovskite NCs with near-unity PLQYs through by nickel ion doping.Noted that it's also the first time to investigate the structure of doped perovskite NCs by a series of microstrucrture analysis methods,such as X-ray absorption spectra.Combined with density functional theory calculations,we have revealed that mid-gap defects in undoped CsPbCl₃ NCs,like Cl vacancies,easily capture exciton and cause low luminescence efficiency,but Ni doping of perovskite nanocrystals can improve local order of the lattice by increase defects formation energy,like Cl vacancies and Cs vacancies,which could restrain the nonradiation process and achieve near-unity PLQYs.